Compatibility for Tropical Aquarium Fish

Written by brenton shields
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Compatibility for Tropical Aquarium Fish
Goldfish should typically only be kept with other goldfish. (fish image by JASON WINTER from

Tropical fish aquariums are popular in many homes. Freshwater fish, while typically easy to care for, have certain compatibility requirements that should not be ignored. Compatibility pertains to what types of fish can be kept with other types of fish, which is important to those wanting variety in their aquariums. Certain groups of fish will typically only do well with each other, while others may not get along or become food for others. Make sure to check the compatibility of all of your fish before deciding to allow them to cohabitate.

Group One: Small Community

Group one consist of tetras, which are small tropical fish that come in a variety of styles and colours, plus a few others. These fish are community fish that typically do well with each other, though they should not be placed with larger fish (as they may become food) or fish with long fins, as they may swarm and nip at fins. These fish include neon and glowlight tetras, rasboras, white cloud mollies, fancy guppies, cory catfish (commonly called "cories"), glass catfish, small honey gouramis and ghost shrimp.

Compatibility for Tropical Aquarium Fish
A cory cat rests at the bottom of an aquarium. (cory image by Holtea Silviu from

Group Two: Intermediate Community

The second group consists of community fish that are typically slightly larger than community fish from group one. This group includes larger tetras, like painted tetras (sometimes called "fruit" tetras), serpae tetras, black neon tetras, danios, swordtail fish, platies and mollies. This group can generally cohabitate.

Group Three: Large Community

These community fish grow to relatively large sizes, requiring an aquarium of at least 29 to 55 gallons. Some of them can also be solitary and relatively aggressive, particularly towards smaller fish. This group includes clown loaches, barbs such as tiger barbs, most large gouramis, and many freshwater sharks like tricolour sharks (also known as "bala" sharks), rainbow sharks, red tail sharks and white tip sharks.

Compatibility for Tropical Aquarium Fish
A gourami stares at the camera. (gourami image by Lucid_Exposure from

Group Four: South American Cichlids

This group is composed of very aggressive animals that should be kept only in small groups in large aquariums. They will readily attack smaller fish, as they eat feeder goldfish and violently defend their territories. These fish will eventually require very large aquariums and should only be kept together under strict supervision. This group includes Jack Dempseys, convict cichlids, firemouth cichlids, flowerhorns, Texas cichlids, Oscars, red devils and midas cichlids.

Compatibility for Tropical Aquarium Fish
A tiger oscar can be very aggressive and territorial. (Red Tiger Oscar image by Mike Price from

Group Five: African Cichlids

This group is divided into two subgroups that should not be mixed. First there are Mbuna cichlids, which are very colourful animals with a unique social hierarchy. However, these fish are highly aggressive towards other groups of fish and should be kept in groups of at least 10 to 12 in large aquariums, typically over 80 gallons or so. These fish include auratus cichlids, red zebras, johannis and kenyis. Secondly there are peacock cichlids, which live in the same lake but away from the Mbuna group, and include peacocks and haps, which also come in a variety of colours. Synodontis catfish, a very large but peaceful catfish, can be kept with both subgroups.

Group Six: Angels

Angel fish are popular in blackwater aquariums, which contain water mimicking that found in the Amazon. Angelfish can be mildly aggressive, and are compatible with other angels and with certain gouramis like neon blue gouramis and dwarf gouramis.

Compatibility for Tropical Aquarium Fish
A marbled angelfish swims by the glass. (angelfish image by pearlguy from

Group Seven: Goldfish

Goldfish are cold water fish, meaning that they do not require a heater. They can also be a little on the dirty side, and should only be kept with other goldfish, though not koi, which need very large aquariums or preferably ponds. Tank-compatible goldfish include orandas, fantails, telescope eyes, and black moors.

Compatibility for Tropical Aquarium Fish
Goldfish are coldwater fish. (Goldfish image by Lucy Cherniak from

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